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Câu hỏi: Tích phân $\int\limits_{0}^{\dfrac{\pi }{4}}{\cos x\text{d}x}$ bằng
A. $\dfrac{\sqrt{2}}{2}-1$.
B. $\dfrac{\sqrt{2}}{2}$.
C. $-\dfrac{\sqrt{2}}{2}$.
D. $1-\dfrac{\sqrt{2}}{2}$.
A. $\dfrac{\sqrt{2}}{2}-1$.
B. $\dfrac{\sqrt{2}}{2}$.
C. $-\dfrac{\sqrt{2}}{2}$.
D. $1-\dfrac{\sqrt{2}}{2}$.
Ta có $\int\limits_{0}^{\dfrac{\pi }{4}}{\cos x\text{d}x}=\left. \sin x \right|_{0}^{\dfrac{\pi }{4}}=\dfrac{\sqrt{2}}{2}$.
Đáp án B.